Lifting jack



FIG. 1 is a front perspective view of one end of a lifting jack showing my new design;

FIG. 2 is a front perspective view thereof of the end opposite to that shown in FIG. 1;

FIG. 3 is a rear elevational view thereof; and

FIG. 4 is a rear perspective view thereof. 

The ornamental design for a lifting jack, substantially as shown. 